Abstract
Hydrogen production from water splitting using solar energy based on photoelectrochemical (PEC) cells has attracted increasing attention because it leaves less of a carbon footprint and has economic superiority of solar and hydrogen energy. Oxide semiconductors such as ZnO possessing high stability against photocorrosion in hole scavenger systems have been widely used to build photoanodes of PEC cells but under visible light their conversion efficiencies with respect to incident‐photon‐to‐current conversion efficiency (IPCE) measured without external bias are still not satisfied. An innovative way is presented here to significantly improve the conversion efficiency of PEC cells by constructing a core–shell structure‐based photoanode comprising Au@CdS core–shell nanoparticles on ZnO nanowires (Au@CdS‐ZnO). The Au core offers strong electronic interactions with both CdS and ZnO resulting in a unique nanojunction to facilitate charge transfer. The Au@CdS‐ZnO PEC cell under 400 nm light irradiation without any applied bias provides an IPCE of 14.8%. Under AM1.5 light illumination with a bias of 0.4 V, the Au@CdS‐ZnO PEC cell produces H2 at a constant rate of 11.5 μmol h−1 as long as 10 h. This work provides a fundamental insight to improve the conversion efficiency for visible light in water splitting.
Highlights
Nanowire arrays directly grown on F-doped SnO2 glass. c,d) TEM images with different magnifications of Au@CdS-ZnO. e) high-resolution transmission electron microscopy (HRTEM) image showing the detailed structure of Au@CdS core–shell on ZnO
The photoanode is composed of core–shell Au@CdS nanoparticles anchored on ZnO nanowires (Au@CdS-ZnO) that were grown on F-doped SnO2 glass, a transparent and conducting substrate
The Au@CdS nanoparticles with an average size of 10 nm are uniformly distributed on the surface of ZnO nanowires (Figure 1c,d) while having a well-defined core–shell structure, in which the Au core locates between the ZnO and CdS (Figure 1e and Figures S2 and S3, Supporting Information)
Summary
Since using a TiO2 photoanode to split water by Fujishima and Honda, researchers have been attempting to develop effiany applied external bias is still lower than 10.0%.[14,15,16,17,18,19,20] One reason for the low conversion efficiency is the limited charge transfer rate resulting in relatively high charge recombination.[21,22] The development of photoanodes with favorable structure/junction to direct charge transfer for highcient photoanodes for photoelectrochemical (PEC) water split- efficiency PEC water splitting cells is essential. We develop a core–shell structure to facilitate conversion efficiency, photoanodes should effectively harvest charge transfer of ZnO-based photoanode, which comprises core–. Li Chongqing Key Laboratory for Advanced Materials and Technologies of Clean Electrical Power Sources Chongqing 400715, P.R. China. The core– shell structure of Au@CdS is found to form a desired nanojunction between CdS and ZnO to greatly promote charge transfer, significantly enhancing the IPCE efficiency of the PEC cells to 14.8% measured with a two-electrode configuration and without any applied bias. The efficiency is much higher than that of 9.5% for PEC cells in the absence of the core–shell structure, and is the best among all ZnO-based two-electrode PEC cells. Yang School of Chemical and Biomedical Engineering Nanyang Technological University Singapore 637457, Singapore
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